HETEROGENEITY IN CELLULAR-RESPONSE AND INTRACELLULAR-DISTRIBUTION OF CA-2+ CONCENTRATION DURING AND AFTER METABOLIC INHIBITION

Study objective - To characterise cell injury during myocardial hypoxia and reoxygenation, [Ca2+]i was measured in Guinea pig ventricular myocytes using digital images of fura-2 fluorescence.Design - [Ca2+]i and cell morphology were measured during and after the perfusion of 2 mmol·litre-1 sodium cyanide (NaCN).Experimental material - 28 ventricular myocytes isolated from Guinea pig hearts.Measurements and main results - Eight out of 28 cells became rounded during the perfusion with NaCN, and [Ca2+]i increased from 48 (SEM 6) nmol·litre-1 to 163(24) (p<0.0l) before cell rounding, and to 311(46) (p<0.0l) after cell rounding. Ten cells were rounded after the washout of NaCN, and [Ca2+]i increased to 252(41) nmol·litre-1 before cell rounding (p<0.0l), and to 314(48) after cell rounding (p<0.0l). Intracellular distribution of [Ca2+]i was heterogeneous in some cells with high [Ca2+]i. The values of [Ca2+]i before and after cell rounding, during and after the perfusion of NaCN, were significantly lower than those during the perfusion of strophanthidin (0.1 mmol·litre-1).Conclusions - There appeared to be a mixed population of myocytes, some showing normal [Ca2+]i and shape, and others showing high [Ca2+]i and contracture, during the perfusion or the washout of NaCN. Ca2+ overload alone is unlikely to be the main and the only mechanism of cell injury during myocardial hypoxia/reoxygenation. Other mechanisms such as membrane disturbance could be involved.